This invention relates to a process for preparing liquid polyamides from nitriles, water and amines. In one embodiment, this invention relates to the preparation of polyamides from dinitriles, diamines and water.
There are several known methods for producing polyamides by contacting nitriles, amines and water. At an early date in the development of nylons, it was proposed that linear polyamides be made by heating a reaction mixture comprising a dinitrile, a diamine and water. This process is disclosed in Greenwalt, U.S. Pat. No. 2,245,129. The procedure disclosed in the Greenwalt patent is carried out in two stages, the first stage comprising the heating of the reaction mixture in a closed reaction vessel until a low molecular weight polyamide is formed, and the second stage comprising subsequent heating of the precursor or prepolymer that is produced to form a higher molecular weight polyamide. Later patents, such as U.S. Pat. No. 3,847,876 provide for an improved process for preparing high molecular weight polyamides by contacting a dinitrile, a diamine and water. This patent teaches that an improved process results from conducting this reaction in the presence of ammonia in three stages.
The invention described herein discloses a simple process which can be conducted in one or two stages to produce an amide from a nitrile, an amine and water. The key to the instant process is the discovery that carbon dioxide will act as a catalyst to increase the yield and selectivity of the product. Moreover, when the nitrile is a dinitrile and the amine is a diamine, a high quality polyamide having good molecular weight can be prepared.